1. Field of the Invention
The invention relates to a method of producing a fiber-reinforced, three-dimensional product by using a mold in which the product is formed.
2. Description of Related Technology
Methods of forming fiber-reinforced, three-dimensional products of plastic material and reinforcing fibers by molding a planar laminate are known. However, in such prior methods, during production of a three-dimensional shape, the formed planar laminate is not fixed in the mold in which it is deposited. If short or cut fibers are used for reinforcement of the plastic material, the material will normally not be fixed.
As a result, it is not possible to control the orientation and distribution of the fibers when the product is given a three-dimensional shape. Thus, the finished, three-dimensional product will not always have well-defined material properties throughout the product.
Methods are also known wherein the planar laminate is fixed partially in all directions, so that displacement of the deposited material is possible when it is given a three-dimensional shape.
Such potential for displacement in the material means that the orientation of the reinforcement fibers in the end product does not correspond to the orientation that the reinforcement fibers are given in the deposited planar laminate before a three-dimensional shape is applied to it. Thus, in the three-dimensional end product there may be a larger distance between individual reinforcement fibers than when the fibers are deposited in the planar laminate. Thus, at the same thickness of material throughout the surface of the product, the percentage content of reinforcement fibers will fall, decreasing as the molded distance from the planar original laminate increases. As a result of this lower content of reinforcement fibers, the strength will decrease in such parts of the finished product.
The production of a three-dimensional product may take place by depositing a number of layers on a three-dimensional shape, such as described, for example, in U.S. Pat. No. 4,404,156 and U.S. Pat. No. 5,312,579. However, for mass production, a method where a planar laminate is formed initially, and subsequently given its three-dimensional shape by pressing or deep pressing the laminate, would preferably be used.
WO 95/35200 discloses a method of producing a fiber-reinforced, three-dimensional product including the steps of depositing long fibers in a mold consisting of a frame in which a carrier net for the fibers is suspended. The individual layers of a formed planar laminate are positioned in such a manner that only a first end is secured at a frame side. The first ends of the various layers are secured at different frame sides. By this method it is possible, in a pressing procedure giving a product its three-dimensional shape, to obtain a virtually uniform distribution of the fibers, even in areas which are subjected to the longest distance of movement away from the original planar laminate. Unfortunately, this method allows only deposition of layers and reinforcement material uniformly over the entire carrier net.
U.S. Pat. No. 2,964,442 describes frames for placing reinforcing fibers in a parallel distribution, either uniformly or irregularly, to achieve uniform distribution of fibers in a shaped article. However, U.S. Pat. No. 2,964,442 does not disclose how to control the degree and the position of reinforcement in the shaped article.
Therefore, a need exists for a method which allows manufacture of fiber-reinforced, three-dimensional shaped products having defined areas of higher reinforcement.